(1) Field of the Invention
The invention concerns electric supplies and in particular voltage regulator converters.
(2) Prior Art
The U.S. Pat. No. 4,943,903 to Gilbert Cardwell discloses a voltage regulator converter receiving a continuous unregulated voltage on input and providing a continuous regulated voltage on output. This converter is illustrated in FIG. 1. This converter presents a main transformer T1 presenting two primary windings E1 and E2 and secondary windings illustrated by E7. The converter presents in addition a transformer T2, containing primary windings E5 and E6 and secondary windings E3 and E4. The primary windings E1 and E2 of the transformer T1 are coupled between an unregulated source voltage Vin and the secondary windings E3 and E4 respectively of transformer T2.
A square wave signal generator includes a command SWG controlling two NMOS transistors Q1 and Q2 respectively, each arranged in series between a local ground and the windings E3 and E4. The voltage between primary windings E5 and E6 of the transformer T2 is controlled by a regulator fed by the terminal Vin and comprising capacitor C, inductance L, diode D3 and transistor Q1. The diodes D1 and D2 permit isolating the primary windings of the transformers T1 and T2. The windings E7 are connected to a rectifier assembly whose output voltage is measured. This output voltage level is provided to the input of a regulation device R1 which modifies the conduction cyclic ratio of the transistor Q3 according to the voltage level measured. The output voltage level is regulated as follows: the second transformer selectively subtracts from the primary terminals of the main transformer a part of the series voltage applied.
This converter presents disadvantages: transistors Q1 and Q2 switch when the current that crosses them is non zero and the opening of these transistors takes place when their drain-source voltage is non zero, causing a decrease in the converter performance. In addition, this solution only applies for a square wave push-pull converter.